Telegraphy and radiotelegraphy



Y. MARREC TELEGRAPHY AND RADIOTELEGRAPHY June 26, 1928.

Filed April 1925 Patented June 26, 1928.

UNITED STATES PATENT OFFICE.

YVES MARREC, or. LoNnoN; ENGLAND, ASSIGNOR T MARREC LIMITED, or LoNnoN,

- ENGLAND.

TELEGRAPHY AND RADIOTELEGRAPHY.

Application filed April 2, 1925, Serial N0. 20,069, and in Great BritainApril 14, 1924.

This invention relates to ordinary telegraphy along wires and towireless telegraphy, of the type 1n whlchsignals of differentfrequencies are transmltted simultane- 5 ously, and has for its object amethod of this type in which the signals have several differentfrequencies which are relatively near to each other.

In the systems of transmission of the type referred to hithertoemployed, a relatively large frequency difference between the signals toavoid perturbations caused by resultin g beats whose intensity is muchgreater than theintensity of the individual signals, 1 s em-. ployed.This is a drawback, as an aerial or transmission line adapted to acertain frequency does not give so goodresults with other frequencies.The intern'nttent nature of the beats Was also a greater obstacle thanif the beats had been permanent.

According to this invention, applicant produces by any suitable means atthe sending end (line, cable or aerial), as many different frequenciesas there are signals WllICll it is desired to transmit simultaneously,provided that the said frequencies differ from each other by at leastoscillations per second and that none of'the beats caused by thesesimultaneously transmitted oscillations of different frequencies havethe same frequency as one of the frequencies separately used for thetransmission of different signals, the latter having as much as possiblethe same intensity.

Applicant also transmits at the sending end during the spacing periodsupplementary compensating oscillations for each distinct frequency usedfor signalling, in order to maintain permanently the heats which,although modified in period, are nevertheless not. modified enough todisturb the signals as they do when they are intermittent, theoscillations of said spacing frequencies bemg approximately of the sameintensity as the frequencies used for signalling.

In order to modify, not the electrical conditions, which remain constantactually, but only the frequency of the signals, for producing theintervals between the signals, the frequencies of the compensation orspacing oscillations must be very near their signalling frequencies, butthey must be at least of the order of 10* above or below the. signallingfrequency,

The different signalling frequencies can also be very near, of the orderof difference 20 on the condition that beats will be' produced by thesesignalling frequencies, corresponding to one of them. For the receptionthe receivers corresponding to each different signalling frequ so as toehminate the cu ency are disposed rrents to the frequencies of whichthey are not'tuned, for

instance by utilizing to t1 1is end a selective receiving system asdescribed in applicants co-pending specification Serial No. 656,450.\Vith such a receiving system, the intermittent objectionable currentsare not received, but they have the drawback of cutting the signals ifthey occur at the same time, this being due to the fact tha t thedesired currents and the objectionable currents neutralize one anotherand do not ger effect described in th specification Serial No. .6

produce the trige said co-pendmg 56,450. However,

if a permanent current of invariable intensity is available, the

period of which is only slightly altered while remaining alwayssufficiently different from which the selective circuit ficient toadjust the point the frequency to is tuned, it is sufat which thetrigordinary telegraphy, or o n the same aerial,

in the case of wireless telegraphy, the multiQ plex reception afterdetection, by as many selectors in parallel as there are messages to'receive shnultaneously each selector operating only under the action ofthe currents to which it is tuned, in a limit of about 10 above or belowits resonance frequency.

If originally arranged so that no beats are produced, and the currentthen obtained is kept constant irrespective of the frequency, thefrequencies -are var amount.

then no beat will be produced if all ied by the same In the case ofradio-telegraphy, for instance, WlllCll one can utilize any wave lengthWlll function at the same time as a carrier wave for the severalmodulation waves 1n multlplex .transmission and as a transmission waveon thi length, by changing slight s particular wave ly thewave length tobridge the intervals between the signals. Besides this ordinary highfrequency transmission, for each simultaneous transmission, twomodulation waves will be used, corre. sponding to each separatetransmission, one of these modulation waves being a compensation wave,as described above. For instance, with five transmissions superposed tothe carrier wave, one may have the follOWlIlg arrangement Z FrequencyFrequency Transmission. 0! 12: 3:38";

signals. Spaces In the case of a line transmission, there is, of course,no carrier wave.

Referring to the drawings filed herewith, which illustratediagrammaticall as an example, the arrangement for multiplex workingjust described ni -m, are the five modulators; s,-s are the fiveselectors; t,--t are the corresponding transmitters modifying thefrequencyof the modulators; 0 -0 are the capacities which may, or maynot be short circuited, in order to alter the transmitted frequencyaccording as to whether the key of the corresponding transmitter ispressed down or not.

In the case of line or cable transmission,

- the line is connected to the terminals a and a, the terminals b bbeing earthed. In the case of wireless transmission, the terminals a bare connected to the modulation circuit of the transmitter for multiplexreception at one station, the terminals (1? b are connected to theordinary receiver instead of the tele sages transmitted simultaneously,use may also be made of inaudible frequencies above the audiblefrequencies; in this case it will be sufficient to utilize, forreceiving them, selectors tuned to these inaudible frequencies, using,if necessary, a local heterodyne for producing beats which will bedetected for the production of audible signals.

In orderto utilize the process advantageously, it is advisable to usethe receivers referred to above so as to use frequencies very close toone another to avoid occupying in the case of wireless telegraphy, agreat range of wave lengths which would be objectionable in view ofother foreign communications. As a very sharp selection is obtainablewith these systems, however, differences of received frequencies of theorder of 15- would be sufficient, this constituting a range notexceeding whichwould cause no more perturbations to the foreigncommunications than if one utilized a single frequency in the presentconditions. 'lhe'signals are selected as explained above, and recombinedto constitute the message.

What-I claim and desire to secure by Letters Patent is v 1. Asystem oftelegraphy along lines or of wireless telegraphy, of the type described,in which, for each signal frequency used, a spacing frequency istransmitted for the purpose of sustaining the signaling beats andavoiding the disturbance .due to their otherwise intermittent character.

A system of line or-wireless telegraphy as claimed in claim 1, furthercharacterized in that a compensating wave is transmitted between thesignals, the frequency of which compensating wave is very near thefrequency of the corresponding signal, but not less than 10 above orbelow the latter.

3. A system of line or wireless telegraphy as claimed in claim 1. inwhich a compensating wave is transmitted between the sig nals, thefrequency of which compensating Wave is very near the frequency of thecorresponding signal, but not less than 10- above or below the latter,further characterized in that the different signalling frequencies arevery near to each other, but do not differ by less than 20-, providedthat none of the signaling beats produced by these frequenciescorrespond to one ofthe frequencies itself."

In testimony whereof, I aflix my signa- 'ture.

YVES MARREC.

Ill

